This invention relates to an improved support device, in general, and in particular a device such as a mattress pad for providing different degrees of support responsive to variable loading conditions, even with a uniform patterned support surface.
Numerous conventional support devices comprise a pad or the like formed of synthetic foam which elastically deforms to cushion a load received on the pad. For example, rectangular foam pads of uniform thickness have been used as mattress-like cushions for supporting the body of a person. Since some parts of the body (such as the chest or buttocks) are heavier than other, such parts compress the pad more than do the lighter extremities. Uniform thickness pads (having uniform support characteristics) are known for their tendency to exert uneven pressures on different parts of the body, especially resulting in relatively higher pressure on the heavier body portions. It is also generally known that certain levels of pressure exerted on a person's body by a support pad at the areas of contact therebetween, for given periods of time, tend to restrict proper blood circulation to those areas, which could lead to decubitus ulcers (bed sores).
In one typical approach to such problems, convoluted pads with dimpled surfaces are used to support a body. Such pads have numerous peaks which extend from the surface of the pad into contact with the patient to be supported. Each peak of a convoluted pad acts much like a separate cushion, thereby providing more variable support than a uniform rectangular resilient pad. While offering improved variable support over a uniform pad, the convoluted pad, too, may still tend to restrict circulation in the body at the points which are in contact with the peaks, again leading to decubitus ulcers.
Uniform thickness pads with slits cut into their support surface are also part of conventional efforts for providing improved patient support. Such slits in a pad create numerous sections which can act relatively independently to provide variable support. Use of a slitted pad having a flat contact surface may to some extent avoid the concentrations of pressure on a patient found adjacent to the peaks of a convoluted pad. However, variable or differential support adequate to prevent decubitus ulcers may still not be maintained. Also, with relatively narrow slits between adjacent sections, frictional engagement between such sections can interfere with fully independent operation of the sections. Such side-to-side frictional engagement of adjacent sections can also result in the transmission of shear forces to a patient received on such sections.
Furthermore, all of the above-mentioned pad types may tend to generally preclude adequate or desired ventilation of the underside of a patient which is in contact with the pad. Ventilation is necessary to aid in the healing of any wounds which may be present on the patient, and to generally improve the comfort of the patient by carrying away perspiration, thereby cooling the body.
The prior art contemplates numerous further surface features in efforts to improve patient support, such as holes through a pad or channels formed in a pad. In manufacturing such pads, various complicated cutting steps are often required, demanding skilled manual handling of the pad or sophisticated equipment, and producing a significant amount of waste material, which adds to manufacturing costs. Even greater manufacturing complexity is involved with some prior art pads which attempt to provide improved differential support of a patient by having multiple zones of different support surface features. See, for example, Rogers (U.S. Pat. No. 3,885,257) and Evans (Great Britain specification 1559851). The added complexity comes about from having to treat, cut, or otherwise process the pad differently to form each of its different zones.